Prior art inductive coin detectors are known, for example, from Great Britain 2,151,062. An inductive coin detector comprises a flat coil in the circuit of a high-frequency oscillator. An alternating magnetic field emerging from the coil penetrates a coin channel perpendicularly. A coin rolling through the alternating field in the coin channel changes the resonance frequency of the oscillator as a result of the alternating effect of the coin with the alternating field. The frequency deviation caused by the presence of the coin is used as a measure of the parameter to be measured, such as diameter, alloy, presence in general, etc. The coil is wound from wire or is produced on a printed circuit by etching a copper lamination. The remaining part of the high-frequency oscillator placed at a distance is connected to the coil via feeders screened against signal interference.
Flat coils which can be produced according to various technical methods are known from U.S. Pat. No. 4,494,100 whereby electric conductive material in the form of a single-layer coil is applied on a flat body made of an insulation material. The coil is bonded at the edge of the insulation material and at the center of the coil.
A method is furthermore known in the manufacture of integrated circuits (IC) by which micro-chips are mounted together with the integrated circuit on supports which are punched out together with connection legs from a strip of sheet metal. After being punched out the sheet metal strip has so-called "lead frames" in a regular sequence, each with a support and with the predetermined number of connection legs. The "lead frames" remain connected on both sides via continuous border strips to the positioning holes. This "lead frame" sheet metal strip allows for a low-cost process in outfitting the support with micro chips, in bonding the connections between the integrated circuit and the corresponding connection legs at regular intervals, and in pressing the circuit into an integrated circuit by means of a synthetic material. The completed IC is then punched out of the lead frame.
It is the object of the invention to provide a method of manufacturing an inductive coin detector with low parasitic radiation which can easily be built into a coin tester or the like.